Starting issue - wiring??????
Moderators: GRNSHRK, ron, bfons
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- Posts: 68
- Joined: Wed Feb 13, 2019 4:22 am
- Location: Melbourne, Australia
Starting issue - wiring??????
We all know that older cars are both a joy and a pain to live with. Up until a couple of weeks ago I was, in the most part, in the joy camp but that all changed one day when the car refused to start. Turned over and over and over, etc, etc, etc. and this was completely out of the blue.
Starting with checking the spark plugs for action, ended up finding no spark from coil. After testing the coils vital's I determined it was good. Checked the main and fuel relays and whilst they tested ok, I decided to jumper the wiring block and the car started. Yippee, or so I thought. Put the fuel relay back in first, car started. Put the main relay back in, car started. Again, yippee I thought. Had a celebratory drink and went to bed.
Awoke with plans of a drive (this is just before the full shit storm of Covid-19) and the car just turned over and over and over. Back to square one. Tried the relay jumping trick again and nothing. Bugger.
After doing research I found a few others had suffered similar problems and my conclusion was the ecu could be the culprit, but not knowing anyone with a spare and not being able to get under the dash (kneeling is particularly difficult currently), I palmed the car off to a BMW specialist who, after a couple of weeks of part time looking, narrowed the problem to the wiring to the ecu connector, he thinks. He did check the ecu for any visible issues but nothing stood out as a problem. The car can be started by holding or gently moving the ecu wiring when turning the key. Sometimes it will start again with no intervention and sometime it won't. Sometimes you can move the wires when it is running and it will cough and possibly stall and other times it won't. Is it the connector wiring or the ecu pins, I don't know.
So, the question for those more knowledgeable in this area of problem solving, does it suggest there's a power or earth wire in the loom of a connector or on the ecu that is playing up? As the engine turns over, power is happening to the starter but is there a power feed to the ecu that is not happening or weak? Also, having the ecu loose from its mountings, the same things happen.
As neither the wiring or the ecu had been touched or played with prior to the fault arising, this is really frustrating. The ecu is a Bosch 0261200059.
Any suggestions welcomed.
Starting with checking the spark plugs for action, ended up finding no spark from coil. After testing the coils vital's I determined it was good. Checked the main and fuel relays and whilst they tested ok, I decided to jumper the wiring block and the car started. Yippee, or so I thought. Put the fuel relay back in first, car started. Put the main relay back in, car started. Again, yippee I thought. Had a celebratory drink and went to bed.
Awoke with plans of a drive (this is just before the full shit storm of Covid-19) and the car just turned over and over and over. Back to square one. Tried the relay jumping trick again and nothing. Bugger.
After doing research I found a few others had suffered similar problems and my conclusion was the ecu could be the culprit, but not knowing anyone with a spare and not being able to get under the dash (kneeling is particularly difficult currently), I palmed the car off to a BMW specialist who, after a couple of weeks of part time looking, narrowed the problem to the wiring to the ecu connector, he thinks. He did check the ecu for any visible issues but nothing stood out as a problem. The car can be started by holding or gently moving the ecu wiring when turning the key. Sometimes it will start again with no intervention and sometime it won't. Sometimes you can move the wires when it is running and it will cough and possibly stall and other times it won't. Is it the connector wiring or the ecu pins, I don't know.
So, the question for those more knowledgeable in this area of problem solving, does it suggest there's a power or earth wire in the loom of a connector or on the ecu that is playing up? As the engine turns over, power is happening to the starter but is there a power feed to the ecu that is not happening or weak? Also, having the ecu loose from its mountings, the same things happen.
As neither the wiring or the ecu had been touched or played with prior to the fault arising, this is really frustrating. The ecu is a Bosch 0261200059.
Any suggestions welcomed.
Past toys:
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
Re: Starting issue - wiring??????
Sounds like you're on the right track. I would conduct some point to point continuity testing of all of the ECU wiring to the plug, whilst at the same time moving it to find any faults.. I'm afraid you or someone is going to have to get under that dash and pull the Motronic plug. Other things to check;
1) If an auto, the transmission range switch and associated wiring input to Motronic.
2) All ECU grounds are good.
3) Check the start input to Motronic at pin 4 from ignition switch. She won't start without it.
4) Ignition (from main relay) and continuous feeds to Motronic.
5) Probably a dozen other things I can't remember right now
1) If an auto, the transmission range switch and associated wiring input to Motronic.
2) All ECU grounds are good.
3) Check the start input to Motronic at pin 4 from ignition switch. She won't start without it.
4) Ignition (from main relay) and continuous feeds to Motronic.
5) Probably a dozen other things I can't remember right now
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
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Re: Starting issue - wiring??????
My immediate thought was to try some contact cleaner on the connector block.
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- Posts: 68
- Joined: Wed Feb 13, 2019 4:22 am
- Location: Melbourne, Australia
Re: Starting issue - wiring??????
Nothing like starting a fault finding exercise by working out how to kneel down.
Contact cleaner was my first thought but it may just mask what the real problem is, but it could also prove a quick fix.
If I can get the ecu out from under the dash i should at least be able to play with each wire, and with the car running move each wire individually to see if it plays up. Not knowing the sturdiness of the Motronic unit, is it possible for one of the connectors to become loose or temperamental? Seems strange the problem just appeared out of nowhere and the car, once started can be re-started but left for a bit it wont.
Contact cleaner was my first thought but it may just mask what the real problem is, but it could also prove a quick fix.
If I can get the ecu out from under the dash i should at least be able to play with each wire, and with the car running move each wire individually to see if it plays up. Not knowing the sturdiness of the Motronic unit, is it possible for one of the connectors to become loose or temperamental? Seems strange the problem just appeared out of nowhere and the car, once started can be re-started but left for a bit it wont.
Past toys:
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
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- Platinum Member
- Posts: 4493
- Joined: Tue Mar 16, 2010 8:32 pm
- Location: usually in the barn, Kent, England.
Re: Starting issue - wiring??????
Easiest to remove the steering wheel and front seat, then go in on your back. I’m all for an easy, quick fix.bigboystoy wrote: ↑Sat Apr 11, 2020 4:32 am Nothing like starting a fault finding exercise by working out how to kneel down.
Contact cleaner was my first thought but it may just mask what the real problem is, but it could also prove a quick fix.
Re: Starting issue - wiring??????
Probably showing my ignorance, but would any faults that might cause this kind of thing be stored in the ecu? Or is that only with much more modern cars?
Phil
__________________________
1988 Highline 635 CSi
__________________________
1988 Highline 635 CSi
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- Posts: 68
- Joined: Wed Feb 13, 2019 4:22 am
- Location: Melbourne, Australia
Re: Starting issue - wiring??????
So, I worked out that sitting is a good option and a reasonably comfortable way of working under the dash. Biggest issue is making sure you have all the tools to save getting up and down as your legs are under the door. Still, worked quite well. Also helps to have a mirror and good light to save having to bend in under the dash.
Anyway, before I touched anything I moved the smaller ecu (auto trans???) out of the way and then I tried to start the car and as expected it just turned over and over. Because the cloth tape had been removed from the ecu wiring loom, as I was turning the key I was moving each wire individually but nothing changed, but when I grabbed the full wiring harness, it started. At this stage I was thinking loose plug, not an individual wire. Still, I decided to pull ecu out and check wires fully for possible loose terminal or broken wire in the ecu connector. Also used the multi meter to make sure the wires coming in showed continuity at the terminal. Everything looked good and secure and no broken wires were obvious.
As for the wiring harness, the following tests were done (obtained list from another forum where someone had similar issues)
Continuous power at pin 18 - confirmed 12V
Ignition power at pin 35 - confirmed 11.88V with ignition on
Grounds at pins 16, 17, 19, & 5 - confirmed
Crank position sensor at pins 25 & 26 - measured 994 ohms across pins
Crank speed sensor at pins 8 & 27 - measured 993 ohms across pins
Fuel Pump Relay at pin 20 - confirmed 11.89V with ignition on
Ignition output at pin 1 - confirmed continuity between socket for pin 1 and connector at coil.
Start Input on pin 4 - measured 0.07V with key in ON position. 9.66V with key in start position cranking engine.
So with everything suggesting nothing was out of place, broken or questionable, I plugged the ecu back in and, yes you guessed it, the car started. Now with everything hanging down and the plug cover removed I was able to pull and move each wire and nothing happened. No coughs or splutters, the car just sat and idled.
So where does this leave me, well I've left things as they are and will give it another try tomorrow to see it it starts. If it continues its current form it shouldn't start after a rest, but, as this problem has been a right pain in the side it'll probably start first go just to give me the middle finger salute.
If it does start, I'll put it all back together with a quick spray of contact cleaner just for good measure. If it doesn't, I might just look for a box of matches.
Anyway, before I touched anything I moved the smaller ecu (auto trans???) out of the way and then I tried to start the car and as expected it just turned over and over. Because the cloth tape had been removed from the ecu wiring loom, as I was turning the key I was moving each wire individually but nothing changed, but when I grabbed the full wiring harness, it started. At this stage I was thinking loose plug, not an individual wire. Still, I decided to pull ecu out and check wires fully for possible loose terminal or broken wire in the ecu connector. Also used the multi meter to make sure the wires coming in showed continuity at the terminal. Everything looked good and secure and no broken wires were obvious.
As for the wiring harness, the following tests were done (obtained list from another forum where someone had similar issues)
Continuous power at pin 18 - confirmed 12V
Ignition power at pin 35 - confirmed 11.88V with ignition on
Grounds at pins 16, 17, 19, & 5 - confirmed
Crank position sensor at pins 25 & 26 - measured 994 ohms across pins
Crank speed sensor at pins 8 & 27 - measured 993 ohms across pins
Fuel Pump Relay at pin 20 - confirmed 11.89V with ignition on
Ignition output at pin 1 - confirmed continuity between socket for pin 1 and connector at coil.
Start Input on pin 4 - measured 0.07V with key in ON position. 9.66V with key in start position cranking engine.
So with everything suggesting nothing was out of place, broken or questionable, I plugged the ecu back in and, yes you guessed it, the car started. Now with everything hanging down and the plug cover removed I was able to pull and move each wire and nothing happened. No coughs or splutters, the car just sat and idled.
So where does this leave me, well I've left things as they are and will give it another try tomorrow to see it it starts. If it continues its current form it shouldn't start after a rest, but, as this problem has been a right pain in the side it'll probably start first go just to give me the middle finger salute.
If it does start, I'll put it all back together with a quick spray of contact cleaner just for good measure. If it doesn't, I might just look for a box of matches.
Past toys:
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
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- Posts: 68
- Joined: Wed Feb 13, 2019 4:22 am
- Location: Melbourne, Australia
Re: Starting issue - wiring??????
Ok. It started. Possibly good news but will wait and see.
Used contact cleaner on a brush and gave the ecu terminals a quick clean and did the same on the connector plug. Put the cover on and remounted the ecu in place and yes the car started. Will leave the smaller controller off for the meantime until I test it over the coming days to satisfy myself it will start each and every time.
Still, cannot drive it now anyway so no big issue but would just like to have the uncertainty out of the way.
Used contact cleaner on a brush and gave the ecu terminals a quick clean and did the same on the connector plug. Put the cover on and remounted the ecu in place and yes the car started. Will leave the smaller controller off for the meantime until I test it over the coming days to satisfy myself it will start each and every time.
Still, cannot drive it now anyway so no big issue but would just like to have the uncertainty out of the way.
Past toys:
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
Re: Starting issue - wiring??????
That voltage seems low to me and should be around 12v in start position. There could be bad or intermittent contacts on the ignition switch.bigboystoy wrote: ↑Mon Apr 13, 2020 6:17 am Start Input on pin 4 - measured 0.07V with key in ON position. 9.66V with key in start position cranking engine.
1986 635csi LOCUTUS / Arktis Blau Metallic / Pearl Beige / S38B36/ Close ratio dogleg 5sp
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
2002 E46 M3 / Topaz Blau Metallic / Black Nappa / 6 speed SMG software tuned / Bilstein PSS10 Coilovers / CMP RACP reinforcement
-
- Posts: 68
- Joined: Wed Feb 13, 2019 4:22 am
- Location: Melbourne, Australia
Re: Starting issue - wiring??????
Just a quick update for any that might be interested.
After a week and a bit of the car just sitting, I took a chance and used it on Friday, for the day. I used it as my work transport for the day and covered 150km thru the suburbs and stopped and started it 8 times and the good news is it didn't let me down, not even a hint of a mis-start. So, have I fixed the problem? I hope so. Do I know what the problem was? No, not really. Could it be an issue in the future? Possibly.
At this stage I'll put it down to old wiring connections needing a good clean.
After a week and a bit of the car just sitting, I took a chance and used it on Friday, for the day. I used it as my work transport for the day and covered 150km thru the suburbs and stopped and started it 8 times and the good news is it didn't let me down, not even a hint of a mis-start. So, have I fixed the problem? I hope so. Do I know what the problem was? No, not really. Could it be an issue in the future? Possibly.
At this stage I'll put it down to old wiring connections needing a good clean.
Past toys:
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi
1979 Volvo282GT
1988 Porsche 944S
Current toy:
1986 635 CSi